If an attack occurs before your on-chain insurance expires, the key to filing a claim is providing evidence that proves two things: the policy was active at the time of the attack, and you actually suffered asset loss. On-chain transaction records are far more convincing than screenshots.
According to Nexus Mutual's claims process, you need to prepare materials covering three areas: event description, proof of loss, and ownership verification.
Record Basic Attack Event Information
In the 'Event Details' section of the claim form, you need to clearly describe how the attack happened. You must provide: the exact time of the attack (block height is more precise), the attack type (smart contract exploit, oracle manipulation, etc.), the name of the affected protocol and the specific asset. On-chain links are crucial – attach the link to your original deposit transaction and the transaction during the attack, so the claims assessors can verify directly. Completion standard: Your description lets anyone reproduce the state of your assets on-chain at the time of the attack.
Prepare Proof of Loss
Prove how much asset you actually lost in the attack. For on-chain losses, provide your wallet address, a comparison of holdings before and after the attack (screenshots or on-chain records). If the attack caused protocol suspension or liquidity depletion and you can't complete a withdrawal, you can still file a claim – but attach the protocol announcement or on-chain state proof. Nexus Mutual requires most policies to have provided a prior loss proof at the time of purchase or before the loss occurs. Completion standard: You have a verifiable record of asset loss.
Risk reminder: InsurAce requires you to submit complete loss and ownership proof within 7 days after filing a claim, otherwise it will automatically be deemed invalid and rejected. Nexus Mutual also has a 14-day cooling-off period; you must wait until the cooling-off period ends before formally submitting a claim. If you miss the deadline, the window closes and cannot be reopened.
Verify Wallet Ownership
Prove that you indeed control the wallet address that suffered the loss. Most on-chain policies require you to pre-sign a wallet signature at purchase; this signature record is stored as prior ownership proof in a private database. If you completed this step at purchase, you don't need to repeat it during the claim. If off-chain proof is needed, the app will prompt you for the additional information required. Completion standard: Your wallet address matches the ownership information tied to the policy.
Submit the Claim and Upload Materials
Submit your claim through the insurance protocol's app while the policy is active or within 35 days after expiry. On Nexus Mutual's 'Your Covers' page, find the relevant policy and click Claim. Upload an IPFS hash or attachment, and note that a claim deposit is required (Nexus Mutual charges 0.05 ETH, refunded if the claim is approved, not refunded if denied). Completion standard: Your claim application has been successfully submitted and an on-chain record has been generated.
Common Reasons for Claim Rejection
When submitting evidence, providing only screenshots without attaching the on-chain transaction hash makes it impossible for the assessors to independently verify the loss. Another issue is missing the submission window – failing to record in time after the attack, so that by the time you want to submit, the cooling-off period hasn't passed or the claim window has already closed.
Next Steps Guidance
As soon as an attack happens, go to a blockchain explorer and take screenshots of the affected address's transaction records, including the original deposit transaction hash and balance changes before and after the attack. Then log into the insurance protocol app, find the policy under 'Your Covers', and follow the steps to fill in the event details and upload the materials. Before submitting, we recommend contacting a claims assessor via the in-app chat function to have them confirm that your materials are complete.
